TJC 08 TJC H1 Prelim Paper 1(with ans)

TEMASEK JUNIOR COLLEGE Preliminary Examinations Higher 1 CHEMISTRY 8872/01 Paper 1 Multiple Choice 19th September 2008 50 minutes Additional materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Write your name, CG and index number on the Answer Sheet in the spaces provided. There are thirty questions on this paper. Answer all questions. For each question, there are four possible answers A, B, C, and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. This document consists of 15 printed pages.

2 Section A For each question there are four possible answers, A, B, C and D . Choose the one you consider to be correct. 1 Ethanonitrile, CH 3CN, was boiled with NaOH and the NH 3 gas evolved was passed into 50 cm 3 of 1.00 mol dm -3 of HC l. The excess acid required 26.00 cm 3 of 1.00 mol dm-3 NaOH solution for neutralization. What was the mass of ethanonitrile used? (Mr of CH3CN = 41) A 0.492g B 0.984g C 1.07g D 1.97g 2 Thallium(III) ions can oxidize iodide ions to iodine. 25.0 cm3 of a 0.0480 mol dm -3 solution of T l3+ ions was added to excess potassium iodide solution. The liberated iodine is titrated against 0.106 mol dm -3 sodium thiosulphate. 22.60 cm 3 of sodium thiosulphate solution was required to react with iodine in the following reaction. I2 + 2S2O3 2- → 2I- + S4O6 2- What was the oxidation state of Tl after its reaction with potassium iodide? A -1 B 0 C +1 D +2 3 Which of the following species has an electronic configuration of 1s22s22p63s23p63d5? A Cr+ B Mn C V D Fe2+ TJC 2008 8872/01/PRELIM 2008 [Turn over

3 4 Which of the following has the most number of unpaired electrons? A Al B Co3+ C NO D V2+ 5 In which of the following pairs does the first species have a larger bond angle than the second? A ClO3 -, BrO3 - B SO3 2-, SO4 2- C PCl3, AlCl3 D H2O, H3O+ 6 Antimony, Sb, is in Group V of the Periodic Table. It forms salts which contain the SbF5 n- anion, the shape of which is square pyramidal. What is the value of n? A 2 B 3 C 4 D 5 TJC 2008 8872/01/PRELIM 2008 [Turn over

4 7 Which of the following compounds is the least volatile? A CH3CH2CH2CH2OH B (CH3)3COH C CH3CH2CH2CH2NH2 D (CH3)3CNH2 8 When 0.15 g of magnesium was added an excess of dilute sulphuric acid in a calorimeter (with negligible heat capacity), a maximum temperature rise of 6.2 oC was recorded. What is the enthalpy change for the reaction? (heat capacity of dilute sulphuric acid = 494 J K-1) A - 3.06 kJ mol-1 B - 496 kJ mol-1 C - 632 kJ mol-1 D - 744 kJ mol-1 TJC 2008 8872/01/PRELIM 2008 [Turn over

5 9 Consider the energy cycle below involving propan-2-ol. CH 3CH(OH)CH3(l) + 9/2 O2(g) 3CO2(g) + 4H2O(l) 3C(s) + 4H 2(g) + 5O2(g) Using the following data, calculate ΔHr. enthalpy change of combustion of carbon = -393.5 kJ mol-1 enthalpy change of combustion of hydrogen = -285.5 kJ mol-1 enthalpy change of formation of propan-2-ol = -316.5 kJ mol-1 A -77 kJ mol-1 B -362.5 kJ mol-1 C -1003 kJ mol-1 D -2006 kJ mol-1 ΔHr ΔH2 ΔH1 10 Each of the following equilibria is subjected to two changes carried out separately: (i) the volume of vessel is increased at constant temperature; (ii) the temperature is increased at constant pressure. For which equilibrium will both of these changes result in an increase in the proportion of products? A H 2(g) + I2(g) 2H I(g) ∆H = +53 kJ mol-1 B 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) ∆H = -950 kJ mol-1 C N2O4(g) 2NO 2( g ) ∆H = +57 kJ mol-1 D N2(g) + 3H2(g) 2NH 3(g) ∆H = -92 kJ mol-1 TJC 2008 8872/01/PRELIM 2008 [Turn over

6 11 Compounds Q and R react according to the following equation Q(s) + R(g) U(g) + 2V(g) The value of the equilibrium constant, K C, is 7.3 at 200 °C and 22.8 at 400 °C. Which of the following statements is true? A The production of U and V is an exothermic process. B The activation energy of the forward reacti on is higher than the activation energy of the backward reaction. C The position of equilibrium shifts to the right when more Q is added. D The addition of a catalyst will increase the value of the equilibrium constant, K C. 12 Which set of solutions below will not give a buffer solution when they are mixed? A 50 cm 3 of 0.10 mol dm-3 CH3CO2H and 50 cm3 of 0.10 mol dm-3 CH3CO2Na B 100 cm3 of 0.10 mol dm-3 CH3CO2H and 50 cm3 of 0.10 mol dm-3 NaOH C 50 cm3 of 0.10 mol dm-3 CH3CO2Na and 100 cm3 of 0.10 mol dm-3 HCl D 100 cm3 of 0.10 mol dm-3 CH3CO2Na and 50 cm3 of 0.10 mol dm-3 HCl 13 Hydrofluoric acid, HF, dissociates according to the following equation: HF + H 2O H3O+ + F- Ka = 7.2 × 10-4 mol dm-3 Which one of the following statement is correct when 0.05 mole of HF is dissolved in 1 dm3 of water? A The strength of the H-F bond is weak. B The pH of the resulting solution is 1.30. C The acid dissociation constant, Ka, can be expressed as O] [HF][H ] ][F O [H 2 3 -+ . D Phenolphthalein is a suitable indicator for the reaction between HF and NaOH. TJC 2008 8872/01/PRELIM 2008 [Turn over

7 14 The table below gives data for the reaction between P and Q at constant temperature. Experiment [P] / mol dm -3 [ Q] / mol dm-3 Initial rate / mol dm-3 s-1 1 0.2 0.3 4.0 X 10-4 2 0.4 0.6 1.6 X 10-3 3 0.8 0.6 6.4 X 10-3 What is the rate equation for the reaction? A Rate = k[P]2[Q] B Rate = k[P][Q]2 C Rate = k[Q]2 D Rate = k[P]2 TJC 2008 8872/01/PRELIM 2008 [Turn over

8 15 Compound V is converted into compound Y in three steps: Step 1: V → W ΔH1 Step 2: W → X ΔH2 Step 3: X → Y ΔH3 Overall: V → Y ΔHr The energy profile diagram is as shown: Which of the following is correct? ΔH 1 ΔHr rate determining step A Endothermic Exothermic Step 3 B Endothermic Endothermic Step 3 C Endothermic Exothermic Step 2 D Exothermic Endothermic Step 2 Energy X V W Y Y Extent of reaction TJC 2008 8872/0